This program is designed to analyze the biodynamic membrane features of cells which present antigen to the immune system and to relate this analysis to the antigen's immunogenicity. The three cell systems to be studied are: (1)\antigen-presenting cells (APC) presenting their own alloantigens to histoincompatible T cells; (2)\APC presenting non-constitutive antigens to syngeneic T cells; (3)\tumor cells presenting defined tumor-associated antigens and also non-constitutive antigens to syngeneic T cells. We plan to (1)\isolate special APC and define their ability to present TNP and other antigens to the immune system in a specialized manner, focusing on the induction of an immune response which is relatively resistant to suppression. (2)\Analyze the membrane residence time (MRT) of defined membrane components on these cells and compare them with the MRT of the same components on other APC. The components to be measured include: I-A, I-J, I-E, H-2K, H-2D, IgM, IgD, tumor-associated antigens and foreign non-constitutive antigens. (3)\Determine the subcellular factors which regulate MRT. (4)\Determine the physical form of shed membrane components, in particular, their association with lipids. In this project year, we have found that ultraviolet irradiation of cells causes an accelerated loss of certain cell surface components. The loss caused by irradiation may result in suppression of the immune system. We have also studied biochemically the membranes of normal lymphocytes and tumor lymphoid cells. We have found new proteins which identify normal cells and proteins found only on tumors. We plan to make antibodies to these proteins.